Fixed bug for perfect results, updated README

bin/evaluate

@@ -172,8 +172,12 @@ do
 
 		# Match asterisk at beginning of line to select differences/errors
 		# WARNING: Double quotes are important to preserve newlines!
+		# Only create DIFF files for differences.
 		DIFF=`echo "$OUT" | grep "\*"`
-		echo "$DIFF" > $ResultsDir/Metrics/$FNAME.diff
+		if [ -n "$DIFF" ]
+		then
+			echo "$DIFF" > $ResultsDir/Metrics/$FNAME.diff
+		fi
 		echo "$OUT" | grep -v "\*" > $ResultsDir/Metrics/$FNAME.csv
 
 		# If differences reported, record files with errors, generate visualizations